css - 任何人都可以检查我的下拉菜单的 css 代码，不能将导航菜单居中吗？

Question

我是编码 css 的新手，尝试了与我的问题相关的建议答案，但没有任何效果，任何帮助将不胜感激；我想将我的菜单放在页面的中央，同时保留容器背景覆盖整个可用宽度...

这是我的 html 代码:

   <div id="nav">
    <li><a href="index.htm">Home</a></li>
    <li><a href="about.htm">About</a>
        <ul>
            <li><a href="history.htm">History</a></li>
            <li><a href="about.htm#mission">Mission</a></li>
            <li><a href="about.htm#bod">Board of Directors</a></li>
            <li><a href="location.htm">Location</a></li>
        </ul>
    <li><a href="SFO.htm">Facilities & Services</a>
        <ul>
            <li><a href="#">Services >></a>
                <ul>
                    <li><a href="im.htm">Internal Medicine</a></li>
                    <li><a href="obg.htm">OB-Gyne</a></li>
                    <li><a href="pedia.htm">Pediatrics</a></li>
                    <li><a href="surgery.htm">Surgery</a></li>
                    <li><a href="dental.htm">Dental Care</a></li>
                    <li><a href="rehab.htm">Rehabilitation Medicine</a></li>
                    <li><a href="ent.htm">Otorhinolaryngology(ENT)</a></li>
              </ul>
            <li><a href="facilities.htm">Facilities >></a>
                <ul>
                    <li><a href="lab.htm">Laboratory-Tertiary Level</a></li>
                    <li><a href="i&cc.htm">Intensive & Critical Care</a></li>
                    <li><a href="nnc.htm">Nursery & Neonatal Care</a></li>
                    <li><a href="picu.htm">Pediatric Intensive Care</a></li>
                    <li><a href="pcu.htm">Pulmonary Care</a></li>
                    <li><a href="ecc.htm">Ear Care Center</a></li>
                    <li><a href="hdu.htm">Hemodialysis Unit</a></li>
                    <li><a href="cardio.htm">Cardiac Diagnostics</a></li>
                    <li><a href="rd.htm">Radiology Diagnostics</a></li>
                    <li><a href="obg.htm">OB-Gyne Diagnostics</a></li>
                </ul>
    </ul>
    </li>
    <li><a href="hp.htm">Healthcare Plans</a>
    <ul>
            <li><a href="hmo.htm">Accredited HMOs</a></li>
            <li><a href="executive.htm">Executive Checkup</a></li>
            <li><a href="cc.htm">Credit Cards</a></li>
    </ul>
    </li>
    <li><a href="hcp.htm">Doctors</a>
        <ul>
            <li><a href="#">""</a></li>
        </ul>
    </li>
    <li><a href="career.htm">Careers</a></li>
    <li><a href="archive.htm">Archive</a></li>
    <li><a href="faq.htm">FAQ</a></li>
    <li><a href="faq.htm">Contact Us</a></li>
      </ul>
    </li>
</ul>
</div>

和我的 CSS 代码:

#nav {
    Z-INDEX: 10;
    text-align:center;
    width: 100%;
    height: 20px;
    background: green;  
    position: relative;
    padding:3px;
    font-size: 13px;
    list-style-type:none;
    list-style-position:outside;
    display:inline-block;
    font-weight: bold;
    line-height:1.5em;
    float: none;
 }
#nav-wrapper {
    text-align: center;
 } 
#nav ul{
    Z-INDEX: 10;
    text-align:center;
    position:relative;
    width: 1000px;
    display:inline-block;
    margin:0;
    padding:0;
    background: none;   
    list-style-type:none;
    list-style-position:outside;
    line-height: 1.7em;
    font-size: 13px;
    float: none;
 }

#nav li li{
    Z-INDEX: 10;
    text-align:left;
    display:inline-block;
    margin:0;
    padding:0;
    font-weight: normal;
    list-style-position:outside;
    border-bottom: 0.1em solid white;
    color: #fff;
 }

#nav a:link, #nav a:visited{
    display:block;
    padding:0px 5px;
    color:#fff;
    text-decoration:none;
    background: green;
 }

#nav ul a:hover{
    Z-INDEX: 999;
    background: light-green;
    color: yellow;
    position: relative;
}

#nav li ul a:hover{
    Z-INDEX: 999;
    background: green;
    color: yellow;
    position: relative;
}

#nav li li a:hover{
    Z-INDEX: 999;
    background: light-green;
    color: yellow;
    font-weight: bold;
    position: relative;
}

#nav li a:hover{
    background: light-green;
    color: yellow;
    Z-INDEX: 999;
    position: relative;
}

#nav a:active{
    color: yellow;
    font-weight: bold;
}

#nav li{
    float:left;
    position:relative;
}

#nav ul {
    position:absolute;
    width:14em;
    top:1.3em;
    display:none;
}

#nav li ul a{
    width:14.65em;
    float:left;
}

#nav ul ul{
    top:auto;
    }

#nav li ul ul {
    left:14.65em;
    margin:0px 0 0 10px;
    }

#nav li:hover ul ul, #nav li:hover ul ul ul, #nav li:hover ul ul ul ul{
    display:none;
    }
#nav li:hover ul, #nav li li:hover ul, #nav li li li:hover ul, #nav li li li li:hover ul{
    display:block;
    }

Answer 1

你可以用另一个 div 包裹 #nav。

<div id="wrap">
    <div id="nav"></div>
</div>

从 #nav 中删除 width，并应用以下 CSS:

#wrap {
    background: green;
    text-align: center;
}

jsFiddle here - 它有效。